The present disclosure relates to a light emitting element and a method of manufacturing the same. More particularly, the present disclosure relates to an organic electroluminescence element and a method of manufacturing the same.
In recent years, organic electroluminescence displays (hereinafter referred also to simply as “organic EL displays”) using an organic electroluminescence element (hereinafter referred also to simply as “organic EL element”) have been paid attention to as displays capable of substituting for liquid crystal displays. The organic EL displays are of the self-luminous type, and is characterized by small power consumption. In addition, the organic EL displays are considered to have sufficient response to high-definition, high-speed video signals. In view of these points, developments of organic EL displays for putting them to practical use and commercialization thereof are being conducted vigorously.
In general, an organic EL element has a structure in which a first electrode, an organic layer having a light emitting layer formed from an organic light emitting material, and a second electrode are stacked sequentially. In the organic EL elements, in addition, attempts to control the light generated in the light emitting layer so as to improve the purity of luminescent color or to enhance the luminous efficiency have been made by introducing a resonator structure, that is, by optimizing the respective thicknesses of the layers constituting the organic layer (refer to, for example, WO 01/39554 pamphlet (described as Patent Document 1 hereinafter)).
Here, a problem may arise in connection with the dependencies of chromacity and luminance on viewing angle. That is, as the viewing angle increases, the peak wavelength in the spectrum of light emitted from an organic EL display may be shifted largely or the intensity of the light may be lowered considerably. It is desirable, therefore, to suppress the intensity of resonance to a level as low as possible, or, in other words, to make the thickness of the organic layer as small as possible (refer to the above-mentioned Patent Document 1). Where the organic layer is small in thickness, however, there is a problem that if a particle (foreign matter) or a projected part is present on the first electrode as schematically shown in FIG. 16, the coverage of the organic layer would become imperfect, possibly leading to short circuit between the first electrode and the second electrode. If such a short circuit occurs, in an organic EL display based on the active matrix system, the pixel involving the short circuit constitutes a defective pixel, thereby deteriorating the display quality of the organic EL display. In a passive-matrix type organic EL display, on the other hand, the pixel involving the short circuit would constitute a missing line, thereby again deteriorating the display quality of the organic EL display. Such a problem is exaggerated particularly in large-type organic EL displays, because of severer requirements as to viewing angle characteristics and a reduced number of allowable defects per unit area.
Hitherto, a variety of approaches have been tried to restrain short circuits between the first electrodes and the second electrodes. For instance, Japanese Patent Laid-open No. 2001-035667 (referred to as Patent Document 2 hereinafter) discloses a technology of intermittently providing a high-resistance layer between anodes and an organic film, in a bottom emission type organic EL display. In addition, Japanese Patent Laid-open No. 2006-338916 (referred to as Patent Document 3 hereinafter) discloses a technology of forming anodes in a two-layer structure and setting the layer constituting the anodes nearer to an organic layer to be high in resistance, in a top emission type organic EL display. Further, Japanese Patent Laid-open No. 2005-209647 (referred to as Patent Document 4 hereinafter) discloses a technology of forming cathodes in a two-layer structure and setting the layer constituting the anodes nearer to an organic layer to be high in resistance, in a bottom emission type organic EL display.